Present design of the Steering Mirror Assembly (SMA) for ITER ECHUL

In the ITER Tokamak, four Electron Cyclotron Heating Upper Launchers (ECHUL) are needed to control plasma instabilities at the rational surfaces, most importantly the q = 3/2 and q = 2/1 neoclassical tearing modes (NTMs). Each ECHUL is equipped with a set of fixed mirrors (M1, M2 and M3) and a front steering mirror set (M4). The millimetre waves are reflected from these mirrors. EC beams are grouped in two rows of four beams each. There are two M4 mirrors, called Upper and Lower Steering Mirror Assemblies, that rotate independently to target the locations of the instabilities in real time. The previous design of M4 showed no compliance of the non-actively cooled components like bellows and springs after including the thermal load of the mm-wave stray radiation and direct plasma radiation. This paper reports the main design changes with the objective to reduce the thermal loads on the non actively cooled components. The Upper Steering Mirror Assembly (USMA) is presented here as an enveloping case. The components structural integrity enforcing the ITER Structural Design Code for the In-Vessel Components (SDC-IC) is assessed by finite elements analyses.